fix(05): WR-05 gate public file serving on is_public

lagoon/attach/file_test.go

@@ -37,6 +37,19 @@ func TestFileIsPublicDefaultsTrue(t *testing.T) {
 	}
 }
 
+func TestThumbFileID(t *testing.T) {
+	id, ok := thumbFileID("thumb_42_200_200_0_0_crop.jpg")
+	if !ok || id != 42 {
+		t.Fatalf("thumb id = %d ok=%v, want 42 true", id, ok)
+	}
+	if _, ok := thumbFileID("abc123xyz.jpg"); ok {
+		t.Fatal("original disk_name must not parse as a thumb id")
+	}
+	if _, ok := thumbFileID("thumb_x_200_200_0_0_crop.jpg"); ok {
+		t.Fatal("non-numeric thumb id must be rejected")
+	}
+}
+
 func TestFileSelfRegisters(t *testing.T) {
 	for _, m := range All() {
 		switch m.(type) {